I've had my 08 SL55 for about 3 weeks now. Each time I back down our steep driveway there's a "crunching" noise coming from underneath the car as the it passes over the threshold where the driveway meets the street. The car makes no other sounds like this at any other time and doesn't replicate the event on the return up the driveway (the front wheels are turned the opposite direction, left, upon returning home vs hard right when backing out).

My local mechanic has been unable to duplicate the issue at their shop. My concern is that by continuing to drive the car I might be making something worse.

Any ideas/similar experiences?

Thanks

Bill

I have a 07 sl550 I had the same sort of situation it turned out to be lower control arm bushings

Thank you Dave

Could be front torque strut bushings. Part #211-333-29-14 hydro mount.

Thanks NorCal.
If I turn hard left at bottom of driveway as I'm backing out there is no sound. So I believe the issue is on right hand side of car (front or back is unclear) as that side sees the most stress when backing out and turning hard right as it's on downhill side of plane.
Bill

If you hear or feel a small clunking when you apply the brakes at slow speeds, this may also be a sign of need for the bushing replacement. It's hard to figure out where the noise is coming from. I had the same one way driveway clunk as you (steering to the right), dealer replaced both bushings under warranty and no more clunk. These bushings are hydraulic in construction, so they are hard to discern issues - only things like you are noticing. It could be that only one of your bushings is going bad and it would be a good idea to replace both sides while your at it.

HTH.